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Following on from music theory primer and intervals, this post is about the circle of fifths / fourths.

I’ve said previously that we can move through all the keys systematically and this is how we do it.

If we think of the keys as a circle, then the circle of fifths moves us clockwise around the circle adding one sharp note into the Key for each successive step round the circle, starting with the Key of C major.

Conversely, the circle of fourths moves us anti-clockwise around the circle adding one flat note into the Key for each successive step round the circle. This is shown on the diagram below.

This is what is meant by harmonic context when deciding whether we call a note sharp or flat. As the pattern is circular, most books will say once you moved 7 steps through the circle of fifths it’s easier to think in terms of flats and similarly when you’ve moved 7 steps through the circle of fourths it’s easier to think in terms of sharps. There is also a point where the Keys overlap and these are the Keys of B, F#/Gb and C#/Db. Whether you call these sharp or flat depends on how you use them, more often it’s a case of whichever way is easier to write them.

Don’t worry about these too much, I’ve included the whole circle to show you how it works and realistically, you are probably only likely to use the first 4 Keys in either direction anyway.

I always think in terms of sharps for the circle of fifths and flats for the circle of fourths mainly because I’ve written these out longhand so many times I’ve lost count and found it easier to stick with sharps for circle of fifths and flats for circle of fourths because to me it’s less confusing than switching part way through.

The process for following the circle of fifths is as follows. Start with the Key of C major.

C D E F G A B C

Take the note at the fifth position as your new root note. Sharpen the note at the fourth position and write it in the seventh position (x just indicates a space for now)

G x x x x x F# G

Then take the notes in the sixth, seventh, first, second and third positions and write them in that order starting at the second position of the new scale:

G A B C D E F# G

We now repeat this process. Take the note at the fifth position as your new root. Sharpen the note at the fourth position and write it in the seventh position (x just indicates a space for now)

D x x x x x C# D

Then take the notes in the sixth, seventh, first, second and third positions and write them in that order starting at the second position of the new scale:

D E F# G A B C# D

…and so on. You can check you’ve doing it right because there will always be the same major scale intervals of Tone, Tone, Semitone, Tone, Tone, Tone, Semitone and the starting note for each successive Key is given on the diagram above.

The process for the circle of fourths is as follows. Start with the Key of C major:

C D E F G A B C

Take the note at the fourth position as your new root. Flatten the note at the seventh position and write it in the fourth position (x just indicates a space for now)

F x x Bb x x x F

Then take the notes in the fifth, sixth, first, second and third positions and write them in the second, third, fifth, sixth and seventh positions of the new scale:

F G A Bb C D E F

We now repeat this process. Take the note at the fourth position as your new root. Flatten the note at the seventh position and write it in the fourth position (x just indicates a space for now)

Bb x x Eb x x x Bb

Then take the notes in the fifth, sixth, first, second and third positions and write them in the second, third, fifth, sixth and seventh positions of the new scale:

Bb C D Eb F G

…and so on. You can check you’ve doing it right because there will always be the same major scale intervals of Tone, Tone, Semitone, Tone, Tone, Tone, Semitone and the starting note is given on the diagram above.

I’ve written these out longhand in the tables below, indicating the chords in each Key. I think that it is worth writing the circle of Keys out longhand to start with. It takes some time but helps you become familiar with the different major scales and therefore the major Keys and the chords they contain. Over time you’ll start to remember some of them which can really help provide new avenues for improvisation, songwriting and ultimately (well, hopefully a bit at least) ear training.